Why are the Infinity IRS, Reference 1b, Beta ect speakers passive on the mids and highs?

I haven't finalized on the crossover points yet. On the tweeter 3500Hz to 4000 Hz is good, the low point on the mid is very tough. 150hz to 160hz leaves a gap to the bass modules. As I drop the frequency the sound doesn't change much until the EMIM's start to distort for being too low. I have tried a Tympani panel for mid bass 70hz to 135hz It sounds good but not a great look.
Marc

If I recall correctly,  they are at 125, 700, 3k & 8k....
Does your crossover have a choice of Bessel, Butterworth, Linkwitz Riley etc?  Can you change slope? Meaning 12db per octave, 18, 24...or even 64db per octave? 
Please let me know... type of slope and amount of roll off effect phasing and blending, plus each type of slope sounds different.
Once I get that, I'll give you some basic advice to try. 

I can only change frequency. Slope is 18db/octave. I don't know Bessel, ect... You are correct on the crossover frequencies except I thought it was 140hz not 125hz.

I'm going by memory, I could be wrong... What crossover are you using, I'll look it up.

meaning which electronic crossover are you using?